In a production planning and control system, the various subsystems dealing with planning for resources, identifying the requirements.
for production and ensuring their flow, feedback on actual conditions and performance, will have to be designed and fitted together in a time dimension.
In a manufacturing organization, the following subsystems are interdependent and regularly interact to form an integrated production planning and control systems.
Long term capacity planning (3 to 5 years and above)
Aggregate planning/Master scheduling (actual, half yearly, revision, rolling 2 year plans)
Operative planning/ short term scheduling (quarterly/monthly/weekly)
Shop for planning and control (monthly/weekly/daily/shift plans).
While in the continuous process plants and high volume repetitive production, the capacity planning and aggregate planning sub-systems more or less specify the system fully and the lower level planning is minimal and limited to shipment plans, changes in priorities, sequencing of product mix, deployment of over time or sub-contracting etc. in intermittent manufacturing i.e. job shops and large scale products, etc the lower level planning is crucial and involves considerable detail and documentation for each individual order.
For intermittent manufacturing, the system must be flexible so as to react to new information and significant deviations from the forecasts and higher level plans. Feedbacks on actual conditions must flow upward through the system to ensure that the higher level plans and strategies are based on a realistic assessment of the organization’s ability to produce.
The enclosed exhibits show the information flows in the various sub-systems and their linkages with each other in an engineering manufacturing organization.
Exhibit 1
Shows the information flows in the long term capacity planning sub-system, business trends and long term demand forecasts by marketing, combined with preliminary engineering data and historical need ratios specify the long term production plan and the capacity requirements to support the plan.
These requirements when adjusted with the information on current shop performance, planned productivity improvement measures, policies on subcontracting and ancillary development, etc and the constraints of capital budgets will provide the capacity plans. These plans will cover the manpower plans and skill mix, plant and equipment purchases, modifications and replacements as well as the investments in inventories. The inventory levels will take into consideration the policies on project / product deliveries and the operations cycle time of the project/ products and the stage at which the stocks are to be kept. Long term capacity plants commit the organization to a configuration of manpower, skills and equipment which provide boundaries to lower level planning and constrain the development of more complete, detailed plans closer to the actual dates. If this sub-system is not well designed with the needed information flows, no amount of perfection in the lower level sub-system will be of much use, as major capacity changes cannot be affected at short notice.
Exhibit 2
Shows the master scheduling or aggregate planning sub-system. This forms the basis for the annual budget and the profit plan. Customer order and anticipated orders (sales forecast) are combined with engineering information to generate aggregate lead on different resources at different times. Various techniques PERT, Time cycle charts, Graphical methods and Bar charts are used for this purpose. Combining the planned capacity with current information on shop leads, and aggregate loads, for the various products/ projects and their deliveries are arrived at. The aggregate planning or master scheduling process involves consideration of alternative plans and their costs implications for choosing the best course and adopting the same as the basis for the annual profit plan. The alternatives, within the capacity plan which is predetermined by the previous sub-system, will consider for different periods in the year, sub-contracting, over-time, Inventory build-up, number of shifts for different types of equipment, temporary manning, machinery re-layouts, product mix and what orders to forego and what orders to increase. The master schedule will specify the needed level of utilization of critical resources, the policy guidelines for short term capacity adjustments, and the overall time schedules for starting and completion of projects/ products and major assemblies in respect of the various pre production and manufacturing activities.
Exhibit 3
Shows the information flows in the short term scheduling or operative planning. Within the time frame provided by the master schedule for various products, customer orders are combined with engineering and manufacturing process information to determine the sub assembly and component stocks already available, the net requirements to be manufactured are planned. The possible rejections during manufacture and spares requirement, if any, and pending unfulfilled orders if any, are considered while arriving at net requirements relating to different periods. Start and completion time for each sub assembly and components are arrived at and the process times and lead times are superimposed on the existing available capacities, provision is made for pattern of breakdowns and unavoidable down time, worker efficiency, rejection rates and the planned improvements in these.
The process of watching the due dates for start and completion of sub assemblies and components, with the existing shop loads may lead to one or more of the following processes.
Alter Priorities.
Reduction or increase in batch sizes.
Adjust capacities by additional shifts, sub contracts, over time, temporary hiring of skills, regrouping men, etc within the aggregate plan.
Altering delivery dates in consultation with marketing.One important feature in the design of this sub-system is the extent of centralization vs. decentralized scheduling of components and sub assemblies and load of critical equipment.
A high degree of decentralized scheduling maybe fairly effective if the shops are relatively independent such as a product layout, etc where there is a high degree of inter dependence as in a process layout, the short term scheduling will have to be centralized and the scheduling period, i.e. the period of time over which, a schedule can be considered fixed with very few changes, will have to be short to retain the necessary flexibility. If the system permits long schedule periods and a high degree of de centralized scheduling in such cases, the inter dependent nature of operations will require constant chasing in between shops and it will degenerate into an expediting system needing continual intervention by higher management on routine scheduling decisions.
The fourth sub-system in an integrated production planning and control system is shop floor planning and ensuring upward flow of information on actual conditions and performance. This involves the following process.
Production Authorization.
Translate schedules in to sets of production order papers..
Issue orders to release materials, and tools against the production orders.
Arrange for proper sequencing through appropriate priority decision rules.
Arrange for material handling, coordinating work flow between operations and keep records of work in process (shop stores).
Use appropriate physical systems for workcentre leading, indicating availability of materials and tools, job priority, etc. such as loading boards, pigeon hole tracks against work centers etc.
Simple priority rules will have to evolved and used by shop planners for sequencing jobs on work centers, such as:
Earliest due date.
Minimum slack.Jobs in the order of shortest processing time out of all jobs for the period etc.
Acquire Performance Data and Feedback.
This relates to designing the flow of information in the upward direction and ensuring timely feedback to the higher levels of planning. The system should facilitate reporting in respect of planned events as well as unplanned events.
Relating Performance to Plans.
Data relayed from shop floor is used for comparing actual performance to planned performance. There is no justification for acquiring any data and the related paperwork if it is not used for this purpose. Such an evaluation will generate information such as the following:
Items behind schedule for completion, for starting and for any other events.
Completion of production orders against planned.
Progress of total production against planned, for the period and cumulative, in terms of standard hours/value added/physical units. Etc.
Actual utilization of critical facilities as against the planned utilization.
Shop efficiencies, actual Vs planned.
Utilization of high value materials as against planned.
Corrective Actions.
Identifying significant variations in respect of various performance parameters will lead to corrective actions to be taken at different levels of management.
Short term corrective actions may be confined to:
What course of action to follow for items behind schedule, any additional shift, over time, subcontract, delay other jobs, etc, within the policy frame work and aggregate plans?
Whether special measures are required for improving utilization of critical facilities like higher maintenance effort, relief operators to operate facilities during rest pauses etc to be considered.
What course of action to follow when product quality has dropped to unacceptable levels, withdrawing particular lot of raw material which is unsatisfactory, intensify supervision, change operator, correct machine etc.
Whether special task forces/expeditors are to be appointed.
Whether schedules are to be modified or priorities reviewed etc.
Long term corrective actions are aimed at preventing recurrence of such problems ensuring that organization s’ abilities match requirements, and increasing the effectiveness of the production planning and control system.
The various assumptions incorporated in the higher level plans in respects of capacities, facility utilization,, lead times, sub contract and ancillary skills, etc., will have to be continuously checked with the actual occurrence and appropriate corrective actions taken, wherever necessary, the planning process will have to be improved with the help of the information available on actual performance.
A very important concern in the long term is the design of the production planning and control system itself for its adequacy and flexibility, whether the feedback time lags, or the sensitivity of the systems and amount of control actions are appropriate.
While each sub-system described are to be are designed appropriately for the given manufacturing organization, these have to be fitted together and the linkages between them established for an integrated production planning and control systems.
These requirements when adjusted with the information on current shop performance, planned productivity improvement measures, policies on subcontracting and ancillary development, etc and the constraints of capital budgets will provide the capacity plans. These plans will cover the manpower plans and skill mix, plant and equipment purchases, modifications and replacements as well as the investments in inventories. The inventory levels will take into consideration the policies on project / product deliveries and the operations cycle time of the project/ products and the stage at which the stocks are to be kept. Long term capacity plants commit the organization to a configuration of manpower, skills and equipment which provide boundaries to lower level planning and constrain the development of more complete, detailed plans closer to the actual dates. If this sub-system is not well designed with the needed information flows, no amount of perfection in the lower level sub-system will be of much use, as major capacity changes cannot be affected at short notice.
Shows the master scheduling or aggregate planning sub-system. This forms the basis for the annual budget and the profit plan. Customer order and anticipated orders (sales forecast) are combined with engineering information to generate aggregate lead on different resources at different times. Various techniques PERT, Time cycle charts, Graphical methods and Bar charts are used for this purpose. Combining the planned capacity with current information on shop leads, and aggregate loads, for the various products/ projects and their deliveries are arrived at. The aggregate planning or master scheduling process involves consideration of alternative plans and their costs implications for choosing the best course and adopting the same as the basis for the annual profit plan. The alternatives, within the capacity plan which is predetermined by the previous sub-system, will consider for different periods in the year, sub-contracting, over-time, Inventory build-up, number of shifts for different types of equipment, temporary manning, machinery re-layouts, product mix and what orders to forego and what orders to increase. The master schedule will specify the needed level of utilization of critical resources, the policy guidelines for short term capacity adjustments, and the overall time schedules for starting and completion of projects/ products and major assemblies in respect of the various pre production and manufacturing activities.
Shows the information flows in the short term scheduling or operative planning. Within the time frame provided by the master schedule for various products, customer orders are combined with engineering and manufacturing process information to determine the sub assembly and component stocks already available, the net requirements to be manufactured are planned. The possible rejections during manufacture and spares requirement, if any, and pending unfulfilled orders if any, are considered while arriving at net requirements relating to different periods. Start and completion time for each sub assembly and components are arrived at and the process times and lead times are superimposed on the existing available capacities, provision is made for pattern of breakdowns and unavoidable down time, worker efficiency, rejection rates and the planned improvements in these.
The process of watching the due dates for start and completion of sub assemblies and components, with the existing shop loads may lead to one or more of the following processes.
Alter Priorities.
Reduction or increase in batch sizes.
Adjust capacities by additional shifts, sub contracts, over time, temporary hiring of skills, regrouping men, etc within the aggregate plan.
Altering delivery dates in consultation with marketing.One important feature in the design of this sub-system is the extent of centralization vs. decentralized scheduling of components and sub assemblies and load of critical equipment.
A high degree of decentralized scheduling maybe fairly effective if the shops are relatively independent such as a product layout, etc where there is a high degree of inter dependence as in a process layout, the short term scheduling will have to be centralized and the scheduling period, i.e. the period of time over which, a schedule can be considered fixed with very few changes, will have to be short to retain the necessary flexibility. If the system permits long schedule periods and a high degree of de centralized scheduling in such cases, the inter dependent nature of operations will require constant chasing in between shops and it will degenerate into an expediting system needing continual intervention by higher management on routine scheduling decisions.
The fourth sub-system in an integrated production planning and control system is shop floor planning and ensuring upward flow of information on actual conditions and performance. This involves the following process.
Production Authorization.
Translate schedules in to sets of production order papers..
Issue orders to release materials, and tools against the production orders.
Arrange for proper sequencing through appropriate priority decision rules.
Arrange for material handling, coordinating work flow between operations and keep records of work in process (shop stores).
Use appropriate physical systems for workcentre leading, indicating availability of materials and tools, job priority, etc. such as loading boards, pigeon hole tracks against work centers etc.
Simple priority rules will have to evolved and used by shop planners for sequencing jobs on work centers, such as:
Earliest due date.
Minimum slack.Jobs in the order of shortest processing time out of all jobs for the period etc.
Acquire Performance Data and Feedback.
This relates to designing the flow of information in the upward direction and ensuring timely feedback to the higher levels of planning. The system should facilitate reporting in respect of planned events as well as unplanned events.
Data relayed from shop floor is used for comparing actual performance to planned performance. There is no justification for acquiring any data and the related paperwork if it is not used for this purpose. Such an evaluation will generate information such as the following:
Items behind schedule for completion, for starting and for any other events.
Completion of production orders against planned.
Progress of total production against planned, for the period and cumulative, in terms of standard hours/value added/physical units. Etc.
Actual utilization of critical facilities as against the planned utilization.
Shop efficiencies, actual Vs planned.
Utilization of high value materials as against planned.
Corrective Actions.
Identifying significant variations in respect of various performance parameters will lead to corrective actions to be taken at different levels of management.
Short term corrective actions may be confined to:
What course of action to follow for items behind schedule, any additional shift, over time, subcontract, delay other jobs, etc, within the policy frame work and aggregate plans?
Whether special measures are required for improving utilization of critical facilities like higher maintenance effort, relief operators to operate facilities during rest pauses etc to be considered.
What course of action to follow when product quality has dropped to unacceptable levels, withdrawing particular lot of raw material which is unsatisfactory, intensify supervision, change operator, correct machine etc.
Whether special task forces/expeditors are to be appointed.
Whether schedules are to be modified or priorities reviewed etc.
Long term corrective actions are aimed at preventing recurrence of such problems ensuring that organization s’ abilities match requirements, and increasing the effectiveness of the production planning and control system.
The various assumptions incorporated in the higher level plans in respects of capacities, facility utilization,, lead times, sub contract and ancillary skills, etc., will have to be continuously checked with the actual occurrence and appropriate corrective actions taken, wherever necessary, the planning process will have to be improved with the help of the information available on actual performance.
A very important concern in the long term is the design of the production planning and control system itself for its adequacy and flexibility, whether the feedback time lags, or the sensitivity of the systems and amount of control actions are appropriate.
While each sub-system described are to be are designed appropriately for the given manufacturing organization, these have to be fitted together and the linkages between them established for an integrated production planning and control systems.
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